Impregnated wood and method of effecting the impregnation



Patented Dec. 13, 1927.

UNITED STATES -P'A .0

DONALD B. BRADNER, F WILMINGTON, DELAWARE, ASSIGNOR T0 E. I. DUJIONT DE NEMOURS & COMPANY, 01 WILMINGTON,

WARE.

IMIPREGNATED WOOD AND METHOD OF EFFECTING IMPBEGNATION.

No Drawing.

This invention relates to a process and a liquid for treating wood to effect its preservation and to the resulting product. More particularly, it is concerned with the im- 6 pregnation of wood with a solution of along been recognized as a serious problem.

Numerous attempts have been made in the past to protect piling by impregnating the timber with various toxic substances, but

while this treatment gives excellent" protection' at the start, the toxic substance is leached out within 'a few years and then the timber is attacked. When the toxic substance is dissolved in some difiicultly soluble 26 liquid such as petroleum -or creosote, thelife of the pilingis considerably increased, but even in this case the toxic ingredient will in time be leached out.

I have now found that it .is possible to nating agents for wood. More or less of the 4 toxicant, in most cases, crystallizes out in finely divided particles, as the sulphur cools, but these crystals of toxicant' are-entirely surrounded by solid sulphur and consequently will remain almost indefinitely in wood under .waterwithout being leached out. When the timber is attacked by marine borers the toxicant is exposed and kills the borer.

The presence of the sulphur, in addition to preventing the leaching out of the toxic substance, also serves to render the wood water resistant. Moreover, it has been found that the stren h of wood is increased bythe absorption 0 the molten sulphur.

The exam le furnished below discloses in detail a pre erred application of our process. It is to be understood, of course, that it is merely an illustration, and that the details thereln specified, as proportions, tem

scope of the claims.

dissolve many toxic materials in molten sul-* phur and to use these solutions as im'preg-- Application filed November 19, 1925. Serial No. 70,187.

peratures, etc, may

Example: Approximately 2% of arsenic DELAWARE, AfCORPQRATION 0;! DEL'A- I be varied" within the sulphide is heated with 98%.sulphur to-a temperature of approximately 13014.-0 C.,

at which temperaturethe melt is a mobile liquid. The Wood is then impregnated with i this liquid, for example, "by the ordinary vacuum and pressure processfor wood impregnation, maintaining the'tempe rature at approximately 130 C. during'this operas tion. After the desired degree of impregnation has been obtained the excess liquid is removed and, after co'oling, a product is obtained which is. both stronger and more resistant 'to abrasion than the original wood i and which will remain unattacked by marine borers for an indefinite perio stituted for the arsenic sulphide, the only limitation to their use bein that they must be sufiiclently soluble in mo ten sulphur and sufliciently' .toxic' to-be effective. Arsenic. disulphide dissolves to the extent of- 3.3% -1Il sulphur at 140 6.; 4.7% arsenic pentasulphide dissolves in sulphur at 140 C; The product obtained by heating arsenious oxide with sulphur (probably arsenic pentasulphide) has approximately this same solubility. Selenium is soluble to the extentof- .A number of toxic materials may be sub- 1.9% .at 140 (3., phosphorus pentasulphide.

is-sol u ble to the extent of 1.2% at 140 C.,

potasslum sulphide has a solubility of 1.0%. A wide variety of organic compounds are somewhat soluble in .molten sulphur, and

many of these are extremely toxi'c. The sulphur soluble organic arsenic compounds are excellent examples of such materials which are adapted for our purpose.

Although, 'n the example the well known vacuum and pressure process for woodimpregnation is mentioned, the particular manner of effecting impregnation is no-part of my invention. The impregnation may be perfo'rme'd 'by any of the well known.

methods. 4

WVhile the primary purpose in usingthe new liquid: for wood impregnation-is the protection of marine structures, it is realized that its application to almostany wood preservation problem such as railroad ties, fence posts, telegraph poles, building: tim

. I By reason of the peculiar method of my invention which comprises the use of the molten sulphur as a vehicle fOP'tllO toxic substance, the particles of the latter upon cooling are encased in a protecting coating of sulphur and a permanencyof impregnacomprising a solution of a sulphur-soluble tion is obtained which can'be effected in no other manner LA process of impregnating wood'with a solid-toxic substance which comprises employing molten sulphuras a vehicle forsaid substance. p

2. A process oftrcating wood which com prises dissolvinga toxic sulphide in molten sulphur and.impregnating thewood with said solution. r I a 3. A process of treating wood which co1nprises dissolving a sulphide of arsenic in molten sulphur and impregnating the wood with said solution.

comprising a solution of a sulphur-soluble salt of arsenic. in molten sulphur.

7. A liquid adapted for preserving Wood toxic sulphide in molten sulphur. 8. Wood containing within its pores a linely divided solid toxicant, the particles of which are enclosed in'solid sulphur.

9. Wood having in the interstices thereof a solid 'toxicant which is Wholly protected from exposure to moisture by solid sulphur.

.10. \Vood impregnated with solid sulphur and a sulphur-soluble salt of arsenic.

11.; Wood impregnated with solid-sulphur and a sulphur-soluble organic toxicant.

In testimony whereof I aflix my signature.

DONALD B. BRADNER. 

